The Dark Art of Sub-floor Ventilation

Sub-floor Ventilation (SFV) sounds quite simple in principle; replace humid air from accumulating in the sub-floor space with less humid air to prevent the effects of mould, moisture and possible termite damage to your home / building.

Mould has a negative impact on the building materials and can release neurotoxins and spores affecting the occupants health. However, since most situations are unique it generally requires skill and experience to achieve a satisfactory outcome, utilising correctly specified equipment and configurations.

Do you need SFV in the first place?

If you have a musty odour in your home, don’t assume it’s coming from your sub-floor space. Identify the source of any moisture and check (or have a specialist investigate) to see if there is moisture under your home, if it’s coming from inside (poorly ventilated), or in the roof space (possible leak).

Prevention is better than cure

Sometimes water can pool under your home after heavy rain. This will increase the humidity under your home as it evaporates and hence provide conditions for mould growth. If you are on a sloping block of land, you may need to place a physical barrier to divert water around your home, or install Ag-pipe in a trench on the uphill side to prevent water pooling under your house.

If the moisture rises from a spring, or if it’s unavoidable to prevent water accumulating under your home, you may need to dig drainage to allow the water to run off.

Poor natural Ventilation

With the addition of decks and increased vegetation from gardens and shrubs, the natural cross-flow ventilation under homes can be negatively impacted and the usual humidity released from the ground therefore cannot escape the sub floor space.  Moisture is constantly released into the atmosphere from the earth and is dispersed by the wind. However, when a house is built over the earth without adequate ventilation, there is nowhere for the moisture to go but into the building materials. This can provide conditions for mould growth and potentially termites.

SFV systems utilising low wattage fans and strategically placed duct work can assist in removing damp air and replacing it with drier outside air. This requires a site visit to evaluate the situation.